1. Field of the Invention
The present invention relates to a camera and, more particularly, to a compact camera.
2. Description of the Related Art
Cameras, such as digital still cameras, digital video cameras, still picture cameras, and motion picture cameras, are commercialized and widely used. In these cameras, the image of a photogenic subject formed based on a light beam from the photogenic subject (hereinafter referred to as a subject light beam) incident on a picture taking optical system (hereinafter referred to as an image-pickup optical system) including a plurality of lens units is formed on subject image capturing means placed at a predetermined location, for example, on an image pickup device such as a charge-coupled device (CCD), or a photosensitive surface such as a camera film. A desired subject image is thus captured, and is then recorded in a predetermined recording medium in a predetermined form.
In these conventional cameras, a photographing optical system is typically formed of a plurality of lenses to form the subject image on a predetermined location.
A variety of photographing optical systems for conventional cameras are known. For example, in one photographing optical system, predetermined reflecting means such as a reflective mirror is arranged in an optical path to guide the subject light beam incident on the camera to a predetermined subject image capturing means such as the image pickup device or the camera film so that the optical path is bent to be aligned with a direction approximately perpendicular to the incident light optical path. A variety of cameras having a photographing optical system incorporating the so-called bending optical mechanism has been proposed, for example, in Japanese Unexamined Patent Application Publication No. 9-281578 and Japanese Unexamined Patent Application Publication No. 9-163206.
In the cameras disclosed in Japanese Unexamined Patent Application Publication No. 9-281578 and Japanese Unexamined Patent Application Publication No. 9-163206, reflective means is arranged in the optical path of the photographing optical system through which the subject light beam is transmitted so that the optical path of the subject light beam is bent in its way. This arrangement assures a required optical path length while incorporating a compact design in the camera itself.
The so-called bending optical system with the reflective means arranged in the optical path thereof is advantageous in the miniaturization of the camera.
With electronic equipment such as personal computers in widespread use, the demand for the camera is expected to mount which captures and records the subject image formed by the image-pickup optical system using a CCD (Charge-Coupled Device), and then reproduces the subject image.
This type of camera obtains a video signal by picking up the subject image formed through the image-pickup optical system by the CCD, while displaying the subject image on the photographing screen such as a monitor display or an LCD (Liquid-Crystal Display) in response to the video signal. Some cameras incorporate a recording medium such as a memory card in a detachable manner to store the video signal obtained through an image pickup operation.
Thin design is required of such a camera in an attempt to promote the ease of use, and low-cost and compact design.
To meet the thin design requirement, a variety of techniques have been proposed, such as a thin-design digital camera disclosed in Japanese Unexamined Patent Application Publication No. 10-336496 and a recording and reproducing apparatus disclosed in Japanese Unexamined Patent Application Publication No. 9-163206.
In the technique disclosed in Japanese Unexamined Patent Application Publication No. 10-336496, the digital camera houses within a camera body, an image-pickup optical system, an image pickup apparatus, and a monitor. If the camera body is viewed in the optical axis of the image-pickup optical system, the image pickup apparatus and the monitor do not overlap each other. In other words, a unit having the largest depth dimension is the image-pickup optical system. A thin design is incorporated by arranging no units that stack on the image-pickup optical system in the direction of depth.
Japanese Unexamined Patent Application Publication No. 9-163206 discloses a video camera in which the optical axis of the subject light beam incident on a front lens is bent at a right angle to be guided into a solid-state image pickup device. As discussed in connection with another embodiment with reference to FIG. 4 in that disclosure, an arrangement is disclosed in which an optical system and a circuit board of a VTR do not overlap each other when viewed from the subject end. In this way, the depth, length and height dimensions of the video camera are reduced, thereby generally miniaturizing the video camera.
Japanese Unexamined Patent Application Publication No. 9-116796 has proposed an electronic still camera in which an subject light beam is photoelectrically converted and is then recorded on a thin recording medium. The electronic still camera includes a photographing optical system unit, a photoelectrical conversion unit, and a recording unit in that order from front to back in the center of a camera body which has a width dimension larger than a depth dimension, and a recording medium is housed in the recording unit with the planar surface of the recording medium aligned to be perpendicular to the fore-aft line of the camera body. Furthermore, other camera components are arranged beside these components within the camera body. Specifically, first and second circuit boards as signal processing boards and the recording unit are stacked within the camera to miniaturize the camera.
Because of its high power consumption, an electronic camera must use a large battery, and the fact presents difficulty in the miniaturization of the camera.
To improve portability with compact and light-weight design, the battery must be compact. However, a compact battery means lower power capacity, and its service life is short. In view of a sequence of the camera, at a peak power consumption when a plurality of calculations and actuator driving operations are concurrently performed, the voltage of a power supply significantly drops. The voltage, which has dropped below a predetermined threshold, can be determined as a battery voltage drop, and a normal picture taking operation cannot be performed any longer.
The peak power consumption occurs at a limited timing in the operation sequence of the camera. The battery power is thus determined to be insufficient even if there is still power remaining in the battery in terms of overall battery power.
Photographing optical systems of the camera in general have a photographing optical axis aligned with the fore-aft line of a camera body (in the direction of depth). The overall length of the photographing optical system is the main factor that determines the thickness of the camera body. The longer the overall length of the photographing optical system, the larger the thickness of the camera body. A zoom camera in particular uses a number of lenses, and the overall length of the photographing optical system thereof increases. The thickness of the camera body naturally increases.
The inventors of this invention have proposed that a thin design is implemented by incorporating an axis bending type photographing optical system into a camera body. As disclosed in Japanese Unexamined Patent Application Publication No. 11-196303, a reflective surface, arranged in the optical axis bending type photographing optical system, bends the photographing optical axis so that the optical axis of the light beam reflected from the reflective surface is aligned with the direction of width of the camera. The overall length of the photographing optical system is thus shortened.
The assembly method of the camera needs to be simplified to miniaturize the camera at low costs.
In conventional assembly methods of cameras, a chassis is arranged, a circuit board and an image-pickup optical system are then mounted on the chassis, and then camera outer housings are then mounted to cover these components. This method is widely adopted because of its easiness and because each component in its mounted state on the chassis is easily tested. However, space for the chassis is required. To promote miniaturization and compact design, there is a need for the elimination of the space for the chassis.
To meet such a need, circuit boards may be stacked one on another within outer housing members, and finally, the outer housing members are secured each other. Such a camera has already been proposed.
In view of circuit boards, since an electronic camera has a large scale circuit, a plurality of circuit boards, rather than a single circuit board, are required even if the maximum projectable area of the camera is used. A plurality of circuit boards are thus stacked within the camera. The circuit boards are mutually electrically connected using connectors. Since the number of lines is very large, a board-to-board connector having a number of connection terminals mounted on the surface of each circuit board is useful.
This type of connector has the merit of connecting a number of lines at a time. However, since this connector fixes also mechanical positions between circuits at the same time, the dimensional accuracy of the assembly becomes a concern, particularly during assembly.
Specifically, when a circuit board is fixed inside the outer housing of a camera using screws, an image-pickup optical system unit must also be fixed using screws within the same outer housing. The image-pickup optical system unit typically has an image pickup device adjusted and fixed thereto beforehand. The image pickup device is mounted on an image pickup board. In other words, the circuit board and the image pickup board are assembled and fixed within the camera outer housing. The circuit board must be electrically connected to the image pickup board. The mounting positions of the two boards are typically subject to variations. The two circuits have been conventionally electrically connected to each other using a flexible board to accommodate positional variations of the two circuits.
The photographing optical system using the above-mentioned bending optical mechanism has a structure that allows unwanted rays of light to easily reach a predetermined image-formed position. The unwanted rays of light may include internal reflections of light that take place when a subject light beam incident on a lens is reflected from the inner surface of a retainer of the lens, rays of light excessively obliquely incident on a lens closest to the subject end, and rays of light which are reflected from reflective means in undesired directions.
These unwanted rays of light create noise such as ghost and flare in a captured image, thereby resulting in an image degradation. The camera photographing optical system having an axis bending optical mechanism thus needs means (unwanted rays of light prevention means) for blocking or preventing the unwanted rays of light that cause the image degradation.
However, there is no mention of such unwanted ray-of-prevention means in Japanese Unexamined Patent Application Publication No. 9-281578 and Japanese Unexamined Patent Application Publication No. 9-163206. This suggests that no sufficient consideration has conventionally given to the unwanted rays of light in the photographing optical system having an axis bending optical mechanism.
Specifically, in an ordinary photographing optical system in the conventional camera having no reflective means in which the optical path of the subject light beam is not bent in the photographing optical system, one or a plurality of diaphragm members suffice to block or prevent the unwanted rays of light. The conventional axis bending type optical system thus has unwanted ray-of-light prevention means similar to that employed in the ordinary photographing optical system with the optical path thereof not bent.
The ordinary photographing optical system typically requires a focus adjustment mechanism to focus the subject image at a predetermined position. The focus adjustment mechanism is a mechanism that moves a predetermined lens, out of a plurality of lenses forming the photographing optical system, along the optical axis to move the image-formed position of the subject image.
A reduction in the dimension of the camera in the fore-aft direction, namely, a thin design is preferably implemented in the photographing optical system having the axis bending optical system. To this end, it is effective to shorten a portion of the optical path of a plurality of lenses upstream of the bending point of the optical path, namely, the distance between a front lens unit arranged closest to the subject end and the reflective means.
If a focus adjustment operation is performed by moving the front lens unit arranged upstream of the bending point of the optical path of the subject light beam in the photographing optical system having an axis bending optical mechanism, the number of lens elements in each lens unit and the number of lens units increase. In this arrangement, the thin design is difficult to implement in the camera.
To thin the fore-aft dimension of the camera, the front lens unit is preferably arranged to have a required light collection capability with the minimum number of lens elements.
To meet this requirement in the photographing optical system having an axis bending optical mechanism, it is contemplated that the lens elements in the front lens unit may be set to be stationary in the relative positions thereof, and that a focus adjustment operation is performed by varying the distance between the reflective means and a predetermined component, for example, subject image capturing means such as an image pickup device or a camera film.
In a camera employing an image pickup device as the subject image capturing means, a number of electrical components and circuit boards including connection lines are mounted on the image pickup device. These are typically integrated into a unitary structure.
When the image pickup device is moved with respect to a fixed photographing optical system to perform a focus adjustment operation, components associated with the image pickup device must be mechanically moved together with the image pickup device.
When a camera film is moved to perform a focus adjustment operation with the photographing optical system stationary in a camera using the camera film as the subject image capturing means, a plurality of components for assuring flatness of the camera film must be mechanically moved integrally with the camera film.
In view of the above arrangements, the focus adjustment method by moving the subject image capturing means such as the image pickup device or the camera film in the optical axis of the photographing optical system is not appropriate.
There is no mention of a mechanism performing a focus adjustment operation in the photographing optical system having an axis bending optical mechanism in Japanese Unexamined Patent Application Publication No. 9-281578 and Japanese Unexamined Patent Application Publication No. 9-163206.
The conventional art disclosed in Japanese Unexamined Patent Application Publication No. 10-336496 and Japanese Unexamined Patent Application Publication No. 9-163206 will incorporate a thin design in the camera to some degree. If units are arranged in a manner with no portion overlapping each other, the area size of the camera, when viewed in the optical axis of the photographing optical axis, becomes large. The thin design is thus incorporated at the expense of the area size of the camera. The conventional art is thus not appropriate from the standpoint of promoting the ease of use and thin structure.
In addition to the thin design, a compact structure as a result of the thin design, the ease of assembly and a low-cost design are required of the camera. The above-referenced conventional arts satisfy not all these requirements.
Digital cameras consuming a large quantity of electrical energy are now discussed. Such a camera needs a large space for housing a battery. In the above disclosures, there is no mention of the mounting of a battery that occupies a large space, namely, no mention of any technique that substantially miniaturizes the camera in size.
A battery needs to be miniaturized in a conventional electronic camera to assure portability with compact and light-weight design incorporated. However, a compact camera means a reduction in battery capacity, and then a short service life of battery. In a sequence of camera operation, in a typical control method, the voltage, which has dropped below a predetermined threshold at a peak power consumption timing, can be determined as a battery voltage drop, and the battery power is thus determined to be insufficient even if there is still significant portion of the overall battery power remaining in the battery. A normal picture taking operation cannot be performed any longer.
In Japanese Unexamined Patent Application Publication No. 9-116796, there is no mention of any technique to preclude a problem taking place on a small battery during a peak power consumption. The disclosure also fails to detail any arrangement that is intended to achieve miniaturization, weight balance and the ease of assembly of the camera.
The camera body thickness is thinned using an optical-axis bending type photographing optical system. The use of the optical system alone fails to reduce the width dimension of the camera. The entire camera cannot be reduced in size. To miniaturize the entire camera, not only the thickness thereof but also the width and vertical length thereof (height dimensions) need to be reduced. To this end, other components mounted in the vicinity of the optical axis bending type photographing optical system, for example, a stroboscopic capacitor having a relatively large volume, needs to be effectively mounted in the camera body.
Since a connector using a flexible board, typical of the conventional connection method, has a number of lines as already discussed, the connector itself becomes bulky. The connector is not durable, and is not a reliable connection option. The connector is thus far from improving the reliability and the ease of assembly thereof. The use of the connector does not serve the purpose of the miniaturization of the camera.
Japanese Unexamined Patent Application Publication No. 9-116796 fails to detail the assembly method of the camera. The use of the above-mentioned connector is not satisfactory in terms of the reliability, miniaturization, and the ease of assembly of the camera.
In view of the above problems, the present invention has been developed. The present invention has the following objects.
It is an object of the present invention to provide a camera which includes a photographing optical system with an axis bending optical mechanism using reflective means in the optical path thereof, and forms a subject image in an excellent state thereof on a predetermined image-forming surface by blocking unwanted rays of light, out of light beams incident thereof, unnecessary to form a subject image.
It is another object of the present invention to provide a camera which employs a photographing optical system including an axis bending optical mechanism, and has a compact design with a thin structure in the fore-aft direction of the camera.
It is yet another object of the present invention to provide a camera which features a thin, compact and low-cost structure, and a small projection area size when viewed in the projecting optical axis, and presents the ease of assembly and the ease of use of the camera.
It is still another object of the present invention to provide a camera which is low-cost, generally compact, thin-structured, and easy to use with the projection area size viewed in the projecting optical axis minimized by skillfully arranging a circuit board, an optical system apparatus, and a battery.
It is still further object of the present invention to provide a camera which is low-cost, generally compact, thin-structured, and easy to use with the projection area size viewed in the projecting optical axis minimized by adeptly arranging various types of circuit boards.
It is still another object of the present invention to provide a camera which is compact, and thin, and stable in operation and has an excellent weight balance by arranging a high-capacitance and flat electrical-double-layer capacitor in an layout appropriate for miniaturization.
It is still yet another object of the present to provide an electronic camera having the following advantages.
(a) The height dimension of the camera having an optical axis bending type photographing optical system is reduced.
(b) The camera which is already reduced in size by mounting an optical axis bending type photographing optical system is even further miniaturized.
(c) Dead space in the body of the camera having an optical-axis bending type photographing optical system is effectively utilized.
In accordance with the present invention, a board-to-board type connector is employed in a camera which employs no chassis. The reliability of the connector is therefore enhanced. The electronic camera is thus compact, low-cost, and increases the ease of assembly.